Electrochemical and chemical dealloying of nanoporous anode materials for energy storage applications

Traditionally employed in alloy corrosion studies, dealloying has evolved into a versatile technique for fabricating advanced porous materials. The unique architecture of interconnected pore channels and continuous metal ligaments endows dealloyed materials with high surface-to-volume ratio, excellent electron conductivity, efficient mass transport and remarkable catalytic activity, positioning them at the forefront of nanomaterial applications with significant potential. However, reproducible synthesis of these structures remains challenging due to limitations in conventional dealloying techniques. Herein, this review attempts to consolidate recent progress in electrochemical and chemical dealloying methods for nanoporous anodes in energy storage and conversion applications. We begin by elucidating the fundamental mechanisms driving dealloying and evaluate key factors influencing dealloying conditions. Through a review of current research, we identify critical properties of dealloyed nanoporous anodes that warrant further investigation. Applications of these materials as anodes in metal-ion batteries, supercapacitors, water splitting and photocatalyst are discussed. Lastly, we address ongoing challenges in this field and propose perspectives on promising research directions. This review aims to inspire new pathways and foster the development of efficient dealloyed porous anodes for sustainable energy technologies.

Covalent Organic Frameworks as Single-Site Photocatalysts for Solar-to-Fuel Conversion

Single-site photocatalysts (SSPCs) are well-established as potent platforms for designing innovative materials to accomplish direct solar-to-fuel conversion. Compared to classical inorganic porous materials, such as zeolites and silica, covalent organic frameworks (COFs)─an emerging class of porous polymers that combine high surface areas, structural diversity, and chemical stability─are attractive candidates for SSPCs due to their molecular-level precision and intrinsic light harvesting ability, both amenable to structural engineering. In this Perspective, we summarize the design concepts and state-of-the-art strategies for the construction of COF SSPCs, and we review the development of COF SSPCs and their applications in solar-to-fuel conversion from their inception. Underlying pitfalls concerning photocatalytic characterization are discussed, and perspectives for the future development of this burgeoning field are given.

Atomically Dispersed Catalytic Sites: A New Frontier for Cocatalyst/Photocatalyst Composites toward Sustainable Fuel and Chemical Production

Photocatalysis delivers a promising pathway toward the clean and sustainable energy supply of the future. However, the inefficiency of photon absorption, rapid recombination of photogenerated electron-hole pairs, and especially the limited active sites for catalytic reactions result in unsatisfactory performances of the photocatalytic materials. Single-atom photocatalysts (SAPCs), in which metal atoms are individually isolated and stably anchored on support materials, allow for maximum atom utilization and possess distinct photocatalytic properties due to the unique geometric and electronic features of the unsaturated catalytic sites. Very recently, constructing SAPCs has emerged as a new avenue for promoting the efficiency of sustainable production of fuels and chemicals via photocatalysis. In this review, we summarize the recent development of SAPCs as a new frontier for cocatalyst/photocatalyst composites in photocatalytic water splitting. This begins with an introduction on the typical structures of SAPCs, followed by a detailed discussion on the synthetic strategies that are applicable to SAPCs. Thereafter, the promising applications of SAPCs to boost photocatalytic water splitting are outlined. Finally, the challenges and prospects for the future development of SAPCs are summarized.

Single-site and nano-confined photocatalysts designed in porous materials for environmental uses and solar fuels

Silica-based micro-, meso-, macro-porous materials offer attractive routes for designing single-site photocatalysts, supporting semiconducting nanoparticles, anchoring light-responsive metal complexes, and encapsulating metal nanoparticles to drive photochemical reactions by taking advantage of their large surface area, controllable pore channels, remarkable transparency to UV/vis and tailorable physicochemical surface characteristics. This review mainly focuses on the fascinating photocatalytic properties of silica-supported Ti catalysts from single-site catalysts to nanoparticles, their surface-chemistry engineering, such as the hydrophobic modification and synthesis of thin films, and the fabrication of nanocatalysts including morphology controlled plasmonic nanostructures with localized surface plasmon resonance. The hybridization of visible-light responsive metal complexes with porous materials for the construction of functional inorganic-organic supramolecular photocatalysts is also included. In addition, the latest progress in the application of MOFs as excellent hosts for designing photocatalytic systems is described.

Tris(bipyridine)Metal(II)-Templated Assemblies of 3D Alkali-Ruthenium Oxalate Coordination Frameworks: Crystal Structures, Characterization and Photocatalytic Activity in Water Reduction

A series of 3D oxalate-bridged ruthenium-based coordination polymers with the formula of {[Z^II(bpy)₃][M^IRu(C₂O₄)₃]}_n (Z^II = Zn²⁺ (1), Cu²⁺ (3, 4), Ru²⁺ (5, 6), Os²⁺ (7, 8); M^I = Li⁺, Na⁺; bpy = 2,2’-bipyridine) and {[Zn^II(bpy)₃](H₂O)[LiRu(C₂O₄)₃]}_n (2) has been synthesized at room temperature through a self-assembly reaction in aqueous media and characterized by single-crystal and powder X-ray diffraction, elemental analysis, infrared and diffuse reflectance UV–Vis spectroscopy and thermogravimetric analysis. The crystal structures of all compounds comprise chiral 3D honeycomb-like polymeric nets of the srs-type, which possess triangular anionic cages where [Z^II(bpy)₃]²⁺ cationic templates are selectively embedded. Structural analysis reveals that the electronic configuration of the cationic guests is affected by electrostatic interaction with the anionic framework. Moreover, the MLCT bands gaps values for 1–8 can be tuned in a rational way by judicious choice of [Z^II(bpy)₃]²⁺ guests. The 3D host-guest polymeric architectures can be used as self-supported heterogeneous photocatalysts for the reductive splitting of water, exhibiting photocatalytic activity for the evolution of H₂ under UV light irradiation.

Heterogeneous catalysis and the challenges of powering the planet, securing chemicals for civilised life, and clean efficient utilization of renewable feedstocks

This article reviews, first, the prospects, practices and principles of generating solar fuels. It does so with an analysis of recent progress in the light-driven emission of H2 (and other fuels) as well as O2 from water. To place this challenge in perspective, some current practices entailing the use of well-proven solid catalysts developed for fossil-based feedstocks, are described. The massive differences between proven methods of generating fuel and chemicals from non-renewable and from solar radiation are emphasized with the aid of numerous quantitative examples. Whilst it is acknowledged that a key action in reducing the liberation of greenhouse gases (GHG) is to tackle the challenge of decreasing their evolution in power generation and in the production of steel, aluminium and other bulk commodities (metals, alloys, concrete and ceramics), nevertheless much can be done to diminish the emission of CO2 (and to use it as feedstock) through the agency of new, designed solid catalysts and microalgae. Solar-thermal converters are also attractive alternatives, even though they are more likely to be used centrally rather than in small modular units like 'artificial leaves,' some of which are promising for the purposes of generating energy (and perhaps fuel) in a delocalized, modular manner.

The concept, reality and utility of single-site heterogeneous catalysts (SSHCs)

The large-pores of this metal–organic framework allow bulky reactants to be catalytically converted at single-site active centres situated at the inner surface.

The societal significance of catalysis and the growing practical importance of single-site heterogeneous catalysts

The concept of single-site heterogeneous catalysis, herein defined and extensively illustrated, offers a strategy for the design of new solid catalysts. By capitalizing on the opportunities presented by nanoporous materials to assemble a wide range of new, well-defined, catalytically active centres, it is possible to bring about numerous environmentally benign processes that can replace traditional methods of chemical production. The latter often employs aggressive, corrosive or hazardous reagents. By using both microporous (less than 20 Å diameter) and mesoporous solids (20–500 Å diameter), abundant scope exists for the construction and application of shape-selective, regio-selective and enantioselective catalysts.